# Trouble getting the right Interp Speed with 'FInterp To' node

I was following this course using UE5 version 5.4.2 and building a "Handle Rotation" graph for a door that looks like this:

I encountered this problem: setting the Interp Speed to anything but 0 makes the Return Value wrong.

I mean that, as I understand FInterp, it should eventually return the Target value, but in my case interp speed just makes the value wrong.

For example (Current = 0, Target = 90, Delta Time = World Delta Seconds, Interp Speed = 3) the return value of this is equal to 0.375.

I used event tick to set the delta time but it changes nothing.

Just setting the speed to 0 makes it work, but that is the problem, I want smooth rotation for my door.

• I skimmed the video and made a guess at what graph you were asking for help with - let me know if I used the wrong screenshot. It's not clear to me from reading this question what makes the value 0.375 "wrong" in your mind. What value are you expecting instead, and how do you calculate it? Remember that to make the door rotate gradually, it should not return 90 immediately, but some small increment past Current each tick. So if you wanted it to open at a speed of 3 degrees per second, a return value of 0.375 on the first tick would make sense if your delta time were 0.125 s (8 ticks/sec). Commented Jul 29 at 14:17
• Or, if FInterpTo is using the formula return value = current + (target - current) * (interp speed * delta time) then an output of 0.375 would correspond to a tick rate of 720 ticks per second. Commented Jul 29 at 14:27
• Thank you very much, now I completely understand. My issue was with the value of DeltaTime, which I had set it to WorldDeltaSeconds, even though I hadn’t used EventTick in my EventGraph. Thanks to your explanation, I realized the problem. I’m very grateful to you. Commented Jul 29 at 18:43
• If you've solved your problem, want to write up an Answer post below explaining your new understanding? Commented Jul 29 at 18:44

## 1 Answer

So I was wrong about the value of DeltaTime of FInterp To I hadn't use the EventTick in the EventGraph so setting the DeltaTime to WorldDeltaSeconds wasn't working.

For solution I've set the DeltaTime value to DeltaSeconds of EventTick

• To get markdown formatting on code inline with text, use the backtick mark ` rather than the single quote mark ' Commented Aug 1 at 5:07